Buildings, installations and institutions which have public addressing systems have often also an audio frequency induction loop-system (AFILS). The AFILS system transfers an audio signal through a magnetic coupling to a pick-up coil which can also be called a t-coil, a telecoil or a telephone coil of a hearing aid. The hearing aid, in turn, converts the magnetic signal back into the audio signal of the original information such that the user of the hearing aid can hear the audio signal.
Although the AFILS system is adjusted to provide the user of the hearing aid with good quality audio signals, the adjustment doesn't guarantee a satisfactory overall listening experience to a user of a hearing aid, because the audio signal transfer is susceptible to disturbance and large quality variation in reality. As a result, when a person with a hearing aid comes to a venue such as an auditorium, a concert hall or a church, he/she may notice that the quality of the audio signal is poor in the location of the venue where he/she is prepared to stay. As a result, he/she may start to search for a good place without knowing if he/she can find it at all. Hence, there is a need for improvement.